Beethoven uses many repeating motives throughout his Waldstein Sonata. The exhilarating motive which he opens the piece with exemplifies a very effective use of mixture chords to create a feeling of excitement and go-go. The piece opens with a strong tonic chord and fast moving eighth notes that add to the excitement. The motive builds in the bass with the use of accidentals and passing tones. Each time the bass gets settled it is up rooted again and pushed foreword. The alternations between the mixture chords give the piece a sort of pulling feeling, the dark vs. the light and good.
In the return to this motive in m. 156-170 the sections begin exactly alike. It isn’t until the 12th measure of the motive when things begin to get funky. The closing of this section is extended by none other than... MIXTURE CHORDS!! Instead of repeating the half cadence of the original motive, Beethoven mixes things up and stretches the cadence out, moving from I to bVI to a half-diminished vii7 to a bIII to a iv and finally a V I yeah for PACs!
Go Beethoven and mixture chords!